Method of producing lead frames for electronic components, corresponding component and computer program product

ABSTRACT

An electronic component, such as an integrated circuit, includes at least one circuit having coupled therewith electrical connections including a lead frame of electrically conductive material. The lead frame is produced by an additive process of conductive material, e.g., by 3D printing, by forming a three-dimensional structure of leads having overlapping surfaces with a gap therebetween.

TECHNICAL FIELD

The description relates to electronic components, and more particularly,to producing so-called lead frames in electronic components such ase.g., integrated circuits (ICs).

BACKGROUND

Electronic components, such as integrated circuits (ICs), may includeone or more electronic circuits (e.g., a chip or “die”). These circuitsmay be encased in a package and possibly arranged on a die pad. Thepackage may include a plastics or ceramic packaging (e.g., a moldingcompound or MC) with die pads coupled to pins of the package, with thedie sealed within the package and electrically conductive wires (e.g.,gold) coupling the pads to the pins.

Such wires were once attached by hand. In present-day technology thattask is performed by machines, leading to a lead frame (LF), which is aset of metal leads that extend outside the package/housing to formelectrical connection pins for the component.

Lead frames may be produced with a variety of processes. For instance,lead frames may be etched e.g. by photolithographic processes, by usinglight to transfer a geometric pattern from a photo-mask onto alight-sensitive, chemical “photoresist” layer deposited on a metallicstrip. Once developed, the resist layer may be chemically removed fromall those areas not affected by the exposure pattern and a photo maskremains on the metal surface to protect locally the strip from theetching action of e.g., an acid flow.

Lead frames may also be stamped by creating a frame design on a strip bythe progressive action of plural punches that remove material from thestrip by mechanical action.

Producing a routing to allow dedicated pin-out starting from an existingdevice is difficult with any of those processes.

Such standard technologies do not easily permit leads to be crossed andelectrically insulated. Any “signal crossing” may then be managedthrough wire bonding (which may result in an increase of wire length,wire sweeping and/or reduced wire distance).

Also, the pad layout of the semiconductor (e.g., silicon) may be linkedto lead frame design and creating downsets may involve plasticdeformation obtained with dedicated tooling.

Production technologies based on material removal (chemical/mechanical)thus impose limitations on lead frame design.

Possible drawbacks of conventional processes for producing lead framesbased on chemical/mechanical removal of material may include one or moreof the following:

reduced lead frame design flexibility may not permit to adapt the leadconfiguration to a die with a constrained pad layout;

a device pad layout may be dictated by the desired pad out of the finalproduct and thus require to be customized on that basis;

an existing device may be hardly compatible with different packagetypes, e.g., a die for dual-in-line packages may not be compatible witha single-in-line package;

a dedicated tool may be involved in plastic deformation for each downsetof the frame (tie bar, ground ring, power bar);

managing thickness variations in different frame areas may involvemilling of a coil with limited design configuration; and

controlled and increased lead frame finishing (surface roughness) almostinevitably involves electro plating or etching, selectiveplating/etching managed through masking.

SUMMARY

One or more embodiments may refer to a corresponding component (e.g., amicroelectronic component such as an integrated circuit).

Also, one or more embodiments may refer to a computer program productloadable into the memory of at least one computer configured to drive a3D printing apparatus and include software code portions for executingthe 3D printing steps of the method of one or more embodiments when theproduct is run on at least one computer. As used herein, reference tosuch a computer program product is understood as being equivalent toreference to a computer-readable medium containing instructions forcontrolling the 3D printing apparatus in order to coordinateimplementation of the method according to the embodiments. Reference to“at least one computer” is intended to highlight the possibility for theembodiments to be implemented in modular and/or distributed form.

Contrary to conventional processes involving removal of material, one ormore embodiments may involve producing a lead frame by an additiveprocess, e.g., electrically conductive material being added, rather thanremoved by forming a three-dimensional structure of leads havingoverlapping surfaces with a gap therebetween.

One or more embodiments may rely on the recognition that 3D printing(additive manufacturing or AM) is becoming a common technology, withdimensions, resolution, and pitch becoming increasingly accurate andwith small sizes.

In one or more embodiments, a three-dimensional lead structure may beproduced having overlapped surfaces with a gap therebetween whichprovides electrical insulation, possibly after molding the housingwithout any insulating spacers added.

In one or more embodiments, a final frame with downsets may be createdwithout plastic deformation (e.g., without dedicated tools).

In one or more embodiments, three-dimensional routing may extendcompatibility of an existing device with customized pin out as specifiedby different customers.

One or more embodiments may offer one or more of the followingadvantages:

frame design may be adapted to complex pad layouts with flexibilitycomparable to organic substrates (multilayer routing) since 3D routingis obtained through an additive process;

frames with localized surface modifications in terms of density,roughness and/or porosity may be created “natively” to improve e.g.,resin adhesion;

frames with localized undercuts may be created natively e.g., to enhanceanchoring/adhesion between the package moulding compound and the frame;

a frame may be printed with areas with different thicknesses withoutconstraints, similarly, a power thick slug may be printed as amonolithic part of the frame, thus possibly dispensing with riveting orlaser welding; and

frame thickness may be differentiated to improve wire-to-wire distance(wire looping).

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, purely by way ofnon-limiting example, with reference to the annexed figures, wherein:

FIG. 1 is a schematic representation of one or more embodiments of acircuit coupled to a lead frame;

FIG. 2 corresponds to a cross-sectional view along line II-II of FIG. 1;

FIG. 3 is a schematic representation of one or more embodiments of acircuit coupled to a lead frame;

FIG. 4 corresponds to a cross-sectional view along line IV-IV of FIG. 3;

FIG. 5 is a perspective view showing certain details of embodimentsaccording to FIGS. 3 and 4;

FIG. 6 is an opposing perspective view to FIG. 5 showing certain detailsof embodiments according to FIGS. 3 and 4;

FIG. 7 is a schematic representation of one or more embodiments of acircuit coupled to a lead frame;

FIG. 8 corresponds to a cross-sectional view along line VIII-VIII ofFIG. 7; and

FIG. 9 is an elevational view of a circuit coupled to a lead frame inaccordance with one or more embodiments.

It will be appreciated that, in order to facilitate understanding theembodiments, the various figures may not be drawn to a same scale.

DETAILED DESCRIPTION

In the ensuing description, one or more specific details areillustrated, aimed at providing an in-depth understanding of examples ofembodiments. The embodiments may be obtained without one or more of thespecific details, or with other methods, components, materials, etc. Inother cases, known structures, materials, or operations are notillustrated or described in detail so that certain aspects ofembodiments will not be obscured.

Reference to “an embodiment” or “one embodiment” in the framework of thepresent description is intended to indicate that a particularconfiguration, structure, or characteristic described in relation to theembodiment is comprised in at least one embodiment. Hence, phrases suchas “in an embodiment” or “in one embodiment” that may be present in oneor more points of the present description do not necessarily refer toone and the same embodiment. Moreover, particular conformations,structures, or characteristics may be combined in any adequate way inone or more embodiments. That is, one or more characteristicsexemplifies in connection with a certain figure can be applied to anyembodiment as exemplified in any other figure.

The references used herein are provided merely for convenience and hencedo not define the scope of protection or the scope of the embodiments.

Throughout the figures, embodiments of an electronic component aregenerally indicated as 10.

Such embodiments may include an electronic circuit 12, such as chip (or“die”) arranged in a package 14. The outline of such a package isschematically indicated in dashed line in FIGS. 1, 3, 8, and 9.

In one or more embodiments, the die 12 may be arranged on a die pad 16,which may be arranged within the package or located at the (e.g.,bottom) surface of the package. In one or more embodiments a die pad 16may not be provided.

In one or more embodiments, the package 14 may include a plastics orceramic packaging (e.g., a molding compound or MC).

Also, while one chip/die 12 is shown by way of example in the figures,plural chips/dice 12 may be included in the component 10.

Providing electrical contact to the chip(s) 12 may involve connectingdie pads 18 to pins 20 of the package, and sealing the die 12 within thepackage 14, with electrically conductive wires 22 (e.g., gold)connecting the pads 18 to the pins of the lead frame 20.

The wires 22 were once attached by hand. In present-day technology thattask is performed by machines, leading to the lead frame 20, that is aset of metal leads (e.g. bars) that may extend outside thepackage/housing 14 to form the pins.

The designation 3D printing (or additive manufacturing, AM) coversvarious processes which may be used to produce three-dimensional objectsby means of an additive process. In such a process, layers of materialmay be subsequently laid by way of a “3D printer” which may be regardedas a type of industrial robot. A 3D printing process may becomputer-controlled so that an object with a certain shape/geometry maybe produced starting e.g., from a data source, that is by way of acomputer program product for driving 3D printing apparatus and includingsoftware code portions for executing the steps of a 3D printing methodwhen the product is run on such a computer.

The term 3D printing was originally used to designate (only) thoseprocesses involving sequential deposition of material e.g., onto apowder bed by means of a printer head essentially resembling an ink-jetprinter. The term 3D printing is now currently used to designate avariety of processes including e.g., extrusion or sintering processes.While the term additive manufacturing (AM) may in fact be used in thisbroader sense, the two designations, 3D printing and additivemanufacturing (AM) will be used herein as essentially synonymous.

As used herein, wording such as e.g., “3D printing” and “3D-printed”will therefore designate an additive manufacturing process and an itemproduced by additive manufacturing.

One or more embodiments may rely on the recognition that, while regardedas an intrinsically “slow” process, recent developments of 3Dprinting/AM may exhibit—in connection with materials such as copper,aluminium, steel, various metal alloys—parameters which are compatiblewith producing lead frames of electronic components such as ICs.

One or more embodiments may thus involve producing a set of electricallyconductive (e.g., metal) leads comprising the lead frame 20 for aelectronic component 10 e.g., by way of 3D printing (additivemanufacturing).

The annexed figures are schematic exemplary representations of possibleresults achievable with 3D printing of a lead frame for an electroniccomponent, which may be by any 3D printing/additive manufacturingprocess known in the art.

In one or more embodiments as exemplified in FIGS. 1 and 2, the leadframe 20 produced by 3D printing may include leads crossing a power bar(e.g., at 202) and/or a power bar crossing other power bar supports(e.g., at 204).

As schematically shown in the cross sectional view of FIG. 2, crossedleads produced with 3D printing may be separated (that is, may haveoverlapping, e.g., mutually facing, surfaces with a gap therebetween)and thus be electrically insulated with respect to each other, withoutany dielectric interposer, with an electrically insulating material ofthe package 14 (e.g., a molding resin) possibly acting as an insulatorbetween the overlapping or facing surfaces. In that way, 3Dconfigurations of leads may be produced with 3D printing without downsettooling.

In one or more embodiments, wire looping may be facilitated by differentsecond bonding heights. That is (as schematically shown by way ofexample e.g., in FIG. 9) the lead frame 20 produced by 3D printing mayinclude different bonding heights for the wires 22 bonded between thedie 12 and the lead frame 20.

One or more embodiments as exemplified in FIGS. 1 and 2 may thus exhibitone or more of the following features as provided by 3D printing:

reduction of the lengths of wires 22, with facilitated adaptation offrame design to pad layout (e.g., at 202);

reduced risk of short circuits between wires 22 and power bars e.g., inwire landing zone (e.g. 202);

possibility of connecting crossed power bars to alternated leads (e.g.,204);

wire looping optimization made possible by modifying second bond height(e.g. 206 and FIG. 9).

The foregoing may also apply to one or more embodiments as exemplifiedin FIGS. 3 to 6.

FIGS. 3 to 6 exemplify the possibility, provided by 3D printing in oneor more embodiments, to have e.g., one power bar crossed to a pluralityof leads (e.g., as exemplified at 208 and highlighted in FIGS. 5 and 6).

This again may facilitate wire length reduction due to the possibilityof adapting the frame design to the pad layout.

The risk of short circuits between wires and power bars in wire landingzones may again be reduced, and wire looping optimization may again befacilitated by modifying second bond height.

The foregoing may also apply, in addition to embodiments as exemplifiedin any of FIGS. 1 to 6, also to one or more embodiments as exemplifiedin FIGS. 7 and 8.

FIGS. 7 and 8 (to which what has been disclosed in connection with FIGS.1 to 6 may similarly apply) exemplify the possibility, provided by 3Dprinting in one or more embodiments, to have leads routed under the die12 (e.g., under the die pad 16) to be bonded with pads on the oppositeside of the die 12 as schematically shown at 210.

Once more, this may facilitate wire length reduction due to thepossibility of adapting the frame design to the pad layout 12.

Also, 3D routing of lead under the die (pad) may permit to assemble adie for dual-in-line package in a single-in-line package.

It will be appreciated that, for ease of representation, the die 12 isnot visible in the cross sectional view of FIG. 8.

It will thus be appreciated that one or more embodiments may involveproducing electronic components 10 including at least one circuit 12having coupled therewith electrical connections 20, 22 including a leadframe 20 of electrically conductive material.

In one or more embodiments the lead frame 20 may be produced by way of a(notionally single-step) additive process, involving the addition ofelectrically conductive material (e.g., 3D printing) in order to form athree-dimensional structure of leads having overlapping, e.g., mutuallyfacing, surfaces with a gap therebetween.

In certain figures, such as FIG. 1, 3, 5, 6 or 7, the reference number209 denotes a so-called “dam” bar, shown in dashed line.

In one or more embodiments the dam bar 209 may be formed integral (e.g.,one piece) with the rest of the lead frame 20, e.g., by 3D printing, asa part of a three-dimensional structure by way of an additive process ofelectrically conductive material.

In various embodiments, the dam bar 209 may be e.g., co-planar withother leads in the lead frame 20.

In one or more embodiments, the bar 209 is intended to act in fact as adam by exerting a containment action of the material of the package 14in a molten state when this is molded onto the circuit 10 to provide apackage for the circuit 12.

In one or more embodiments, the bar 209 may be formed integral (e.g.,one piece) with the rest of the lead frame 20 by a common additiveprocess (e.g., 3D printing) of electrically conductive material and thusundesirably “short circuit” adjacent leads in the lead frame 20. In oneor more embodiments, the bar 209 may then be removed, at leastpartially, e.g., by removing the “bridges” extending between adjacentleads in the lead frame.

The (possibly partial) removal of the dam bar 209 may take place in anymanner known in the art e.g., by punching.

FIG. 9, already captioned in the foregoing, further highlights thepossibility, provided by additive processes, such as e.g., 3D printing,of having leads with bonding areas differentiated by bonding heights,which may facilitate optimizing wire loops.

In one or more embodiments, any of the (e.g., 3D printed) lead surfacesmay be provided with modified configurations such as e.g., roughness,porosity, a sculptured pattern such as e.g., a honeycomb pattern, and soon, in order to improve adhesion between the package 14 (e.g., themolding compound) and the lead frame 20.

One or more embodiments having been adopted in producing an electroniccomponent may be detected e.g., via surface analysis of exposed leadsand/or X-Ray analysis of 3D configuration of internal leads.

Without prejudice to the underlying principles, the details andembodiments may vary, even significantly, with respect to what isillustrated herein purely by way of non-limiting example, withoutthereby departing from the extent of protection. The extent ofprotection is determined by the claims that follow.

1-11. (canceled)
 12. A method of producing electronic componentscomprising at least one circuit coupled to electrical connections and alead frame of electrically conductive material, the method comprising:forming the lead frame by an additive process of the electricallyconductive material by forming a three-dimensional structure comprisinga plurality of leads having overlapping surfaces with a gaptherebetween.
 13. The method of claim 12, wherein the lead framecomprises a lead crossing a first power bar in the lead frame with a gaptherebetween.
 14. The method of claim 12, wherein the lead framecomprises a first power bar crossing at least one support for a secondpower bar in the lead frame with a gap therebetween.
 15. The method ofclaim 12, wherein the lead frame comprises a first power bar crossedwith a gap therebetween to a plurality of leads in the lead frame. 16.The method of claim 12, wherein at least one lead in the lead frame isrouted under the at least one circuit.
 17. The method of claim 16,wherein the at least one circuit comprises a die mounted on a die pad,the method further comprising forming the lead frame with at least onelead in the lead frame routed under the die pad.
 18. The method of claim12, wherein the electrical connections comprise a plurality of wiresbonded between the at least one circuit and the lead frame, the methodfurther comprising forming the lead frame with different bonding heightsfor each of the plurality of wires.
 19. The method of claim 12, furthercomprising forming a package of an electrically insulating material forthe at least one circuit, wherein the electrically insulating materialof the package extends between the overlapping surfaces of the leadswith a gap therebetween and configured to provide electrical insulationbetween the leads.
 20. The method of claim 19, further comprising:forming the package by molding the electrically insulating material ontothe at least one circuit; forming the lead frame to include a dam barconfigured to contain the electrically insulating material duringmolding onto the at least one circuit; and at least partially removingthe dam bar from the lead frame after forming the package.
 21. Themethod of claim 12, wherein the lead frame is formed by 3D printing. 22.The method of claim 12, wherein the lead frame comprises at least one ofcopper, aluminium, steel, and metal alloys.
 23. An electronic componentcomprising: at least one circuit; a lead frame having athree-dimensional structure; a plurality of leads having overlappingsurfaces with a gap therebetween coupled to the lead frame; and aplurality of electrical connections coupling the at least one circuit tothe lead frame.
 24. The electronic component of claim 23, wherein thelead frame comprises a lead crossing a first power bar in the lead framewith the gap therebetween.
 25. The electronic component of claim 23,wherein the lead frame comprises a first power bar crossing at least onesupport for a second power bar in the lead frame with a gaptherebetween.
 26. The electronic component of claim 23, wherein the leadframe comprises a first power bar crossed with a gap therebetween to aplurality of leads in the lead frame.
 27. The electronic component ofclaim 23, wherein at least one lead in the lead frame is routed underthe at least one circuit.
 28. The electronic component of claim 27,wherein the at least one circuit comprises a die mounted on a die padand the lead frame having at least one lead in the lead frame routedunder the die pad.
 29. The electronic component of claim 23, wherein theplurality of electrical connections comprise a plurality of wires bondedbetween the at least one circuit and the lead frame, and wherein theplurality of electrical connections having different bonding heights foreach of the plurality of wires.
 30. The electronic component of claim23, further comprising a package of an electrically insulating materialfor the at least one circuit, wherein the electrically insulatingmaterial of the package extends between the overlapping surfaces of theplurality of leads with a gap therebetween and configured to provideelectrical insulation between the plurality of leads.
 31. The electroniccomponent of claim 26, wherein the lead frame comprises a dam barconfigured to contain the electrically insulating material duringmolding onto the at least one circuit.
 32. The electronic component ofclaim 23, wherein the lead frame is formed by 3D printing.
 33. Theelectronic component of claim 23, wherein the lead frame comprises atleast one of copper, aluminium, steel, and metal alloys.
 34. Anon-transitory computer-readable medium storing instructions that, whenexecuted, cause an apparatus coupled to a computing device to performsteps comprising: forming a lead frame by an additive process ofelectrically conductive material by forming a three-dimensionalstructure comprising a plurality of leads having overlapping surfaceswith a gap therebetween.
 35. The non-transitory computer-readable mediumof claim 34, wherein the apparatus comprises a 3D printer.